#include "stdio.h"
#include "math.h"
main()
{
	float b[14]; 
	int i,j;
	b[0]=0;	
	for (i=1;i<=12;++i)
	{
		scanf("%f",&b[i]);
		b[0]+=b[i];
	}
	b[0]=b[0]/12;	
	printf("$%.2f\n",b[0]);
}
